212 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



1. ROT ALA L. 

 1. Rotala ramosior (L.) Koehne. Tooth-cup. 



Low or wet ground; frequent. Aug.-Sept. Eastern U. S. (Ammannia humilis 

 Michx.) 



2. DECODON J. F. Gmel. 



1. Decodon verticillatus (L.) Ell. Swamp loosestrife. 



Swampy ground; rare. Aug. Eastern U. S. (Nesaea verticillata H. B. K.) 

 The stems are 1-2 meters high, and root from the tip when they reach the mud. 



3. LYTHRTJM L. Loosestrife. 



Flowers solitary, axillary, small; stamens not more numerous than the petals; leaves 

 alternate; stems glabrous 1. L. alatum. 



Flowers in dense spikes, large; stamens twice as many as the petals; leaves opposite 

 or whorled; stems pubescent 2. L. salicaria. 



1. Lythrum alatum Pursh. 



Low grounds; frequent along the Potomac. June-Aug. Eastern N. Amer. 

 A tall wandlike perennial; stem angled and often slightly winged. 



2. Lythrum salicaria L. Purple loosestrife. 

 Wet meadows and swamps. June-July. Hunting Creek and perhaps elsewhere. 



Northeastern states; naturalized from Eur. 



4. PARSONSIA P. Br. 



1. Parsonsia petiolata (L.) Rusby. 



Dry soil; frequent. Aug.-Oct. Eastern U. S. (Cuphea viscosissima Jacq.; C. 

 petiolata Koehne.) 



111. MELASTOMATACEAE. Meadow beauty Family. 



1. RHEXIA L. Meadow beauty. 



Stems not angled ; leaves oblong or elliptic, mostly petioled 1. R. mariana. 



Stems square or angled; leaves oval or ovate, mostly sessile 2. R. virginica. 



1, Rhexia mariana L. 



Swamps northeast of Washington? infrequent. Aug. Eastern IT. S. ' 



2. Rhexia virginica L. 



Swamps; frequent. July-Sept. Eastern U. S. 



112. ONAGRACEAE. Evening primrose Family. 



Petals and calyx lobes 2 each; fruit burlike. Leaves thin, opposite; flowers white. 



1. CIRCAEA. 



Petals and calyx lobes 4 each or more; fruit not burlike. 

 Fruit indehiscent, nut like. Leaves alternate; flowers white or pink, in wandlike 

 spikes 2. GATTRA. 



Fruit a many-seeded capsule, opening by valves or by a pore. 

 Calyx tube not prolonged beyond the ovary. 

 Seeds with a tuft of silky hairs; calyx deciduous. Leaves alternate; flowers 

 magenta 3. CHAMAENERION. 



Seeds naked; calyx persistent. 

 Stamens 8-12, in 2 rows. Leaves alternate; flowers yellow... 4. JUSSIAEA. 

 Stamens 4, in 1 row. 

 Leaves opposite; stem creeping or floating; petals none, or small and pink. 



5. ISNARDIA. 

 Leaves alternate; stems erect or ascending; petals conspicuous, yellow. 



6. LTJDWIGIA. 



